﻿function setpng(){
		var ua=navigator.userAgent;
		var ie=navigator.appName=="Microsoft Internet Explorer"?true:false;  
		if(ie){     
			var IEversion=parseFloat(ua.substring(ua.indexOf("MSIE")+5,ua.indexOf(";",ua.indexOf("MSIE")))); 
			if(IEversion >= 7.0){

			}else{
				correctPNG4IE6();
			} 
		}else{
		}
	}
	
function correctPNG4IE6()
{
	//获得全部图片
	var imgs=document.getElementsByTagName("IMG");
	for(var i=0; i<imgs.length; i++){
		var img = imgs[i];
		var imgName = img.src.toUpperCase();
		<!--操作PNG图片-->
		if (imgName.substring(imgName.length-3, imgName.length) == "PNG"){
			var imgID = (img.id) ? "id='" + img.id + "' " : "";
			var imgClass = (img.className) ? "class='" + img.className + "' " : "";
			var imgTitle = (img.title) ? "title='" + img.title + "' " : "title='" + img.alt + "' ";
			var imgStyle = "display:inline-block;" + img.style.cssText;
			if (img.align == "left") imgStyle = "float:left;" + imgStyle;
			if (img.align == "right") imgStyle = "float:right;" + imgStyle;
			if (img.parentElement.href) imgStyle = "cursor:hand;" + imgStyle;
			
			<!--对于隐藏层中的图片，或者其他原因导致图片尺寸无法获得-->
			<!--此时我们需要读取图片的真实大小-->
			<!--以免宽高都为0px而导致图片不显示-->
			var imgTrueWidth=0;
			var imgTrueHeight=0;
			if(img.width==0){
				var imgPng=new Image();
				imgPng.src=img.src;
				imgTrueWidth=imgPng.width;
				imgTrueHeight=imgPng.height;
			}
			
			<!--用<span>替换<img>标签-->
			var strNewHTML = "<span " + imgID + imgClass + imgTitle + " style=\"";
			strNewHTML=strNewHTML+"width:" + (img.width==0?imgTrueWidth:img.width) + "px; height:";
			strNewHTML=strNewHTML+(img.height==0?imgTrueHeight:img.height) + "px;";
			strNewHTML=strNewHTML+imgStyle + ";" + "filter:progid:DXImageTransform.Microsoft.AlphaImageLoader";
			strNewHTML=strNewHTML+"(src='" + img.src + "', sizingMethod='scale');\"></span>";
			
			<!--执行替换-->
			img.outerHTML = strNewHTML;
			i = i-1;
		}
	}
}